1. Technical Field
This disclosure relates to integrated circuits, and more particularly, integrated circuits used in radio equipment.
2. Description of the Related Art
In recent years, radio tuners/receivers have been designed with increasing numbers of features. Specifically, radio broadcast has expanded beyond traditional AM/FM radio, and now includes HD radio, DAB radio and DRM standards. Further, additional frequency spectrum can be used in some radio standards, such as DAB's use of Lband. These new frequency channels add additional hardware complexity to optimize system performance. Finally, multiple antennas can be used to improve the performance of the radio system. Thus, with increasing complexity of radio systems, new architectures are needed to deliver high quality services to the customer.
FIG. 1 (Prior Art) is a diagram illustrating one embodiment of a radio capable of operating multiple tuners concurrently. In the embodiment shown, Tuner #1 includes an amplitude modulation (AM) tuning circuit and an FM tuning circuit. The AM and FM tuning circuits may each include a mixer and a local oscillator. A multiplexer (‘Mux’) is coupled to the outputs of both tuning circuits, and may select one for further processing as the received signal by Tuner #1. Automatic gain control (AGC) circuitry is implemented in Tuner #1, and may provide gain control for the band selected by the multiplexer.
Tuner #1 also includes a loop-through path for the FM input. That is, the FM signal may pass through an LNA and a buffer to an output which is coupled to an input of Tuner #2. Although the signal may pass through both an LNA and a buffer, it is nevertheless not subject to AGC. Instead, the FM signal may be gain-controlled by Tuner #2 after receiving it from the loop-through output of Tuner #1.